It is well known in drilling oil wells, the penetration of the drill bit is influenced by the weight impinging on it. Thus, drill collars (heavy wall drill pipe) are normally made up in the bottom hole assembly to provide weight on the bit.
Also, it is well known in drilling oil wells, to use stabilizers as an aid in drilling a directional hole, as an aid in drilling a straight hole and as an aid in preventing contact between the drill string and the bore hole. Thus, stabilizers are used anywhere along the drill string above the drill bit, but mostly they are made up in the bottom hole assembly with the drill collars.
Until recently, the conventional stabilizer was a sub having fins or blades extending from a body, the body of the sub being made up in the drill string by conventional joints, such as pin and box joints. This arrangement however has several undesirable aspects: it adds tool joint connections to the drill string thereby increasing possible points of failure; it causes variations in drill collar stands which increase trip time and unsafe operation for rig personnel; it requires a special bottom hole assembly thereby increasing drilling costs; and it does not permit adjustment of the stabilizer along the drill string without changing subs thereby increasing drilling costs.
Recently, a lock-on stabilizer has been suggested to solve some of these undesirable aspects. The suggested lock-on stabilizer has a body with externally extending fins or blades, two end caps for connecting to the body, an inside solid locking ring and two outside solid locking rings with a single tapered surface for each outside ring. The stabilizer is connected to the drill string by positioning the inside locking ring inside the body, positioning an outside locking ring on either end of and with the tapered surface facing the inside locking ring. The two end caps are screwed into the body which forces the rings together and connects the stabilizer to the drill string. A major difficulty found with this arrangement is its inability to be reused after once being attached. This difficulty is caused by the inherent inability of the solid locking rings to clamp around a drill string without being deformed.
Accordingly, it is a primary object of the present invention to provide a stabilizer that is rapidly and easily connected and disconnected to a drill string by using a coil spring.
Further, it is an object of the present invention to provide a stabilizer that is rapidly and easily connected and disconnected to a drill string by using a coil spring to fasten the stabilizer to the drill string which aids in absorbing shock and vibrations.
Further, it is an object of the present invention to provide a stabilizer that is simple and inexpensive to construct while permitting releasable connection to a drill string.
Further, it is an object of the present invention to provide a stabilizer which may be added to a drill string without increasing tool joint connections.
Further, it is an object of the present invention to provide a stabilizer which may be removed from the drill string and reused without expensive repairs to the stabilizer.
In accordance with the present invention, a stabilizer is provided which is detachably connected or releasably positioned on a drill string. The stabilizer incorporates a tubular body positionable around the drill string. A coil string having a first and a second end is mounted within the body and around the drill string. An anchoring mechanism is mounted with the body for preventing circumferential movement of the first end of the spring around the drill string and a rotating apparatus is mounted with the body for moving the second end of the spring circumferentially around the drill string. The second end of the spring being releasably anchored by the rotating apparatus relative to the body after the spring has gripped the drill string sufficiently tight to secure the body to the drill string while permitting the second end to be released when desired.